1. Field of the Invention
The present invention relates to a charging apparatus used in a copy machine, a printer and other image forming apparatuses employing an electrophotographic method or a static recording method.
2. Related Background Art
A transfer type electrophotographic apparatus has typically the following means configuration and image forming processes. That is, the apparatus typically comes in such a type that uses a rotating drum as its image bearing body and comprises the steps of: using an electrophotographic photosensitive body made of such a substance as selenium, cadmium sulfide, zinc oxide, amorphous silicon, or an organic photoconductive substance to uniformly charge a surface of that photosensitive body to a predetermined potential by use of charging means; image-exposing the charged photosensitive body by image-exposure means to form a corresponding electrostatic latent image; sticking toner of a developer to that electrostatic latent image by developing means to develop as a toner image; transferring that toner image onto at transfer material; and fixing that toner image using fixing means and then discharge it as an image formed medium (copy or print). In this process, the rotating photosensitive body after the toner image is transferred onto the material to be transferred is removed the transfer material toner by cleaning means (cleaner) and used in image formation repeatedly.
As for a process cartridge capable of detachably attaching to the main body of the printer or the copy machine these process means, i.e. the charging means, the developing means, and the cleaning means as well as the electrophotographic photosensitive body, many such types are known and put to practical use that in the initial settings, members abutting against the electrophotographic photosensitive body and its surrounding process means, especially the former, remain as abutting against that. Furthermore, other such types are known that to prevent nicking by vibration or drop, a protecting member is placed between the electrophotographic photosensitive body and the other abutting members, to activate and deactivate the abutting in a manner interlocked with an operation of attaching detaching of the process cartridge to the printer main body.
In the above-mentioned prior art example, however, the electrophotographic body, especially the photosensitive drum made of an organic photosensitive body is continuously abutted by such members as the cleaning member, the contact charging member, and the developing member, which may give rise to the following variety of problems if they are left or stored unused.
A cleaning blade, having an edge portion, of the above-mentioned cleaning member has a concentrated pressure applied at that edge portion, which produces irregularities in a surface of the photosensitive drum abutting against that edge portion, which irregularities in turn produce undesired stripes in an image when it is created both in normal developing and reversal developing.
Furthermore, a cleaning blade made of rubber etc. of the cleaning member gives the photosensitive drum an abutting force changing with its own deviation and deformation, to have permanent deformation of its own and hence a reduced abutting force, thus being disabled to remove the residual toner etc. on the photosensitive drum and contributing to image contamination.
A roller and a blade of the above-mentioned contact charging member may also have compressive deformation or permanent deformation due to their own abutting, thus giving rise to non-uniform charging or poor imaging.
Moreover, a contact type developing sleeve of the above-mentioned developing member may have compressive deformation at its own abutting nip portion, to have poor toner coating or deviated abutting at the developing portion, thus producing an uneven abutting portion pitch on an image.
To prevent these, for example, even with such a type of the process cartridge to which various process means are attached and detached corresponding to the attachment and detachment of the process cartridge main body, these process means can be exempted from being abutted from a time when it is manufactured to a time when it is used by a user, after which however, no measures can be taken for a long nonuse period, so that the material of these process means must be selected from those not liable to be deformed with difficulty.
Furthermore, such a type of the process cartridge does not suffer from the above-mentioned poor imaging due to neglecting that employs a mechanism of butting the process means only when an image is being formed according to a method of attaching and detaching the photosensitive drum using a solenoid clutch or a method of rotating the photosensitive drum in a direction reverse to that for forming images in order to move the process means. The solenoid clutch and other electric components, however, may bring about higher costs of the apparatus and, the reversal rotation of the photosensitive drum may not permit the cleaning means to remove the residual toner which is in contact with the photosensitive drum.
Moreover, a rotating portion of the developing device for always supplying an appropriate amount of toner to the photosensitive drum is typically synchronized with it in rotation, so that when it is rotated in a reverse direction, the toner may be discharged more than necessary and scattered. A one-way clutch would lead to higher costs, if mounted to guard against this in an attempt to rotate that rotating portion in synchronization only with the image forming rotation of the photosensitive drum.
It is an object of the invention to provide a charging apparatus capable of touching a charging member to and separating it from a body to be charged.
It is another object of the invention to provide a process cartridge capable of contacting a process member with and separating it from a photosensitive body.
It is a further another object of the invention to provide a charging apparatus comprising:
a charging member for coming in contact with the body to be charged to charge the body to be charged; and
contacting/separating means for contacting the charging member with and separating the charging member from the body to be charged,
wherein the contacting/separating means converts a moving force of the body to be charged into a force for contacting/separating the charging member.
It is a further another object of the invention to provide a process cartridge comprising:
a photosensitive body;
a process member, pressure-contacting with the photosensitive body, for acting on the photosensitive body; and
contacting/separating means for contacting the process member with and separating the process member from the photosensitive body;
wherein the contacting/separating means converts a moving force of the photosensitive body into a force for contacting/separating the process member.
The other objects of the invention may be clear upon reading of the following description.